Heretofore, the technical means to form a silicon carbide layer or a gallium nitride (GaN)-based semiconductor layer on a substrate of silicon (Si), silicon carbide (SiC) or the like that excels in electrical conductivity or thermal conductivity has been known (refer to “Silicon-based Hetero Devices,” written by Seijiro Furukawa and Yoshihito Amamiya and published by Maruzen K. K. on Jul. 30, 1991, pp. 91-93). For example, the technique for growing a cubic GaN layer by the Molecular Beam Epitaxial (MBE) method on a SiC film formed as an under layer on a substrate of Si has been disclosed (refer to D. Wang, et al., Journal of Crystal Growth (Holland), Vol. 220, 2000, pp. 204-208).
Besides, the method for more conveniently forming silicon carbide by carbonizing the surface of a silicon substrate with the gas of an unsaturated hydrocarbon, such as acetylene (C2H2) has been known (refer to “Silicon-based Hetero Devices” mentioned above). For example, the means to form a silicon carbide layer by placing a silicon substrate in a molecular beam epitaxial device maintained at a high degree of vacuum equivalent to 10−5 Pa or less of pressure and exposing the surface of the silicon substrate to acetylene gas, thereby carbonizing the surface has been known (refer to T. Sugii et al., Journal of Electrochemical Society, U.S.A. Vol. 137, No. 3, 1990, pp. 989-992).
The problem exists that the semiconductor layer cannot be stably formed. For example, the cubic silicon carbide (3C—SiC) has a lattice constant of 0.436 nm, which is nearly equal to the lattice constant, 0.451 nm, of the cubic GaN. Owing probably to the difference of these compounds in ionicity (refer to “Bonds and Bands in Semiconductors” (Physics Series 38) written by J. C. Phillips, published as Third Printing by Yoshioka Shoten on Jul. 25, 1985, pp. 50-51), the GaN layer formed on the silicon carbide layer copiously contains crystal defects, such as twin crystal and stacking fault. No success has been achieved in producing a GaN layer exhibiting good quality and containing crystal defects only in a small density.
This invention, developed in view of the state of affairs mentioned above, is aimed at providing a method for the formation of a semiconductor layer that is capable of forming on a semiconductor layer made of material, such as a silicon carbide layer, having a small ionicity and a strong covalent bonding property a semiconductor layer of a large ionicity, such as GaN, exhibiting good quality and containing crystal defects only in a small density and a light-emitting diode obtained by using the method for the formation of a semiconductor layer.